1. Technical Field of the Invention
The present invention relates to integrated circuits, especially their fabrication, and more particularly to the production of a contact pad on a region of an integrated circuit.
2. Description of Related Art
At the present time, a contact pad is generally produced on a region of an integrated circuit, for example on the source, drain or gate region of a transistor, or else on a polysilicon line forming a resistor, by silicidation (i.e., the formation of a metal silicide) of the upper part of the region and then, after an insulating material, for example silicon dioxide, has been deposited on the region, by making an opening, commonly called a “via” by those skilled in the art, and filling the via with a metal that will come into contact with the silicided zone. This via will thus allow an electrical connection to be made between the silicided semiconductor region and a metallization level of the integrated circuit.
Such a process has many drawbacks. Among these, mention may for example be made of the complexity and the cost of production, but also the problem of the resistance of the silicide layer and the problem of the interface between the metal silicide and the silicon. This is because, if this interface is not correct this may result in a puncture of the junctions, an increase in the resistance, or even debonding of the metal silicide. The interface between the silicided zone and the metal that fills the via must be perfectly controlled. It is therefore necessary to clean the bottom of a contact after opening the vias, so as to minimize the risks of obtaining an interface of poor quality. Consequently, this further increases the complexity and the production cost.
A need accordingly exists in the art to remedy these drawbacks. A process for producing a contact pad that is radically different from that currently used in the prior art is needed.
There is further a need in the art for a process for producing a contact pad that is extremely simple to carry out, with a very good yield, while in particular dispensing with the step carried out in the prior art of cleaning the bottom of the contact.
There is still further a need in the art for a contact pad having a very low resistance and in any case lower than that obtained in the prior art by silicidation.
There is also a need in the art to decrease the contact resistance without increasing the aperture of the via in order to maintain the integration density of the interconnections.